1. Field of the Invention
The present invention relates to a controller of an internal combustion engine having a function to energize a block heater, which is mounted to the engine, with an external power supply to keep an engine coolant warm while the engine is stopped in cold climate.
The present invention also relates to a cooling system abnormality diagnosis device and a block heater determination device of an internal combustion engine having a function to energize a block heater, which is mounted to the engine, with an external power supply to keep an engine coolant warm while the engine is stopped in cold climate.
2. Description of Related Art
A technology described in Patent document 1 (JP-A-2002-30959) attaches a block heater for freeze prevention to a cylinder block of an engine (an internal combustion engine). A power cord of the block heater is connected to a household power receptacle to energize the block heater while the engine is stopped in cold climate. Thus, the technology keeps an engine coolant warm to prevent the freeze in a cold district.
A technology described in Patent document 2 (Japanese Patent No. 3538545) estimates the coolant temperature based on an engine operation state. The technology compares the estimate of the coolant temperature and a sensing value of the coolant temperature sensed with a coolant temperature sensor respectively with predetermined values. The technology performs abnormality diagnosis of a radiator based on the comparison results.
A user arbitrarily decides whether to connect a plug of the power cord of the block heater to the external power receptacle to keep the engine warm during the engine stoppage. An abnormality diagnosis device on the vehicle side receives no information about existence/nonexistence of energization to the block heater. Therefore, the abnormality diagnosis device on the vehicle side performs the abnormality diagnosis of the radiator based on a behavior of the coolant temperature after a start-up without knowing whether the energization to the block heater exists or not.
However, the behavior of the coolant temperature after the start-up differs greatly depending on the existence/nonexistence of the energization to the block heater during the engine stoppage. Therefore, if the abnormality diagnosis of the radiator is performed based on the behavior of the coolant temperature while totally ignoring the influence of the existence/nonexistence of the energization to the block heater as in the conventional technology, there is a possibility that the abnormality/normality is erroneously diagnosed because of the variation in the behavior of the coolant temperature due to the existence/nonexistence of the energization to the block heater.